1. Field of the Invention
The present invention relates to a turbine blade and, more particularly, relates to a turbine nozzle vane for gas turbine engines, consisting of a supportive metallic core encased by a ceramic blade jacket with spacing therebetween, in which there is provided at least one spanwise-oriented cooling air duct. Inner and outer shrouds or shroud segments are provided, by means of which the turbine vane is suspended from inner and outer structural casing components for, on the one hand, centered positioning and, on the other hand, for limited radial as well as axial thermoelastic flexibility.
In order to attain an improved fuel economy, as well as an enhanced performance of the gas turbine engines, the gas temperatures of especially present-day aircraft gas turbine engines, and also of modern stationary gas turbine plants, are required to be as high as possible.
Through sophisticated cooling concepts which require advanced design and production engineering efforts, the gas turbine engine technology has reached a state in which facilitates operation at turbine entry temperatures which, in part, are already located above the melting point of the turbine blade materials. This is presently achieved only with the aid of highly alloyed and, thus, expensive materials; requiring highly complex production techniques, with an attendant correspondingly high risk as well as mostly through also a considerable demand for cooling air.
2. Discussion of the Prior Art
German Laid-open patent application No. 28 34 864 discloses a rotor blade for gas turbine engines, consisting of a supportive metallic core encased by a ceramic blade jacket with a spacing therebetween. The inventive concept in that instance lies essentially in that the thin-sectioned airfoil engages in a slot of a blade tip plate extending along the circumference of the blade, and in which the tip plate is supported in the turbine disk through at least one rod-shaped or wire-shaped blade core by means of, respectively, one widened tip and, respectively, one widened root of the core.
A disadvantage attendant to this construction, on the one hand, lies in that a relatively large amount of air is required herein in order to cool the blade. On the other hand, in this presently known case, thermal stresses are encountered which are generated by the ceramic blade jacket coming into direct or indirect contact with cooling air.
The foregoing prior art approach also fails to provide adequate protection to the structural metallic blade core from thermal radiation, and in which, besides other considerations, no accurately definable support function can be imparted to the herein employed rod-like or wire-shaped blade core.
Another consideration is that this prior art approach primarily relates to rotor blades and, consequently, is predicated upon other criteria than would be primarily associated with a blade designed to serve as a guide vane.